Distributor Lower Bushing Excessive Wear History

[Gene M.]

Re: Distributor Lower Bushing Excessive Wear History

Gene,

These are shafts sold by all of the aftermarket parts houses, and so, although almost nothing is heard about these wear problems, doesn't necessarily mean that the don't occur. They are shipped with considerable surface roughness. If something is published re: shaft material/surface finish as well as bushing material then I have not been able to find it. It might be one of the best trade secrets being kept by the likes of Dave Fiedler and others. This is absolutely not rocket science, and I firmly believe that it is something fundamental that I am missing. I never would have believed that something as simple and seemingly straightforward as a distributor bushing/shaft R & R would be so involved.

DF: If you're listening, then I expect a kickback.

By the way, there are a couple things that some here may not be aware of:
1. The GM melonized steel gear has different dimple orientation than the original iron gear used on vintage distributors.
2. The "football" for centrifugal advance, atop the reproduction "SHP" shafts were installed incorrectly by aftermarket suppliers. After notifying all of them last summer, as to this situation, I can report that the condition has been rectified by LICS, but not by Paragon.

Interesting about the replacement shafts. I've never used one nor looked at them. Always managed to round up a good used original. The surface being "rough" is odd. I would expect that shaft to be ground to a check 4 finish. Should appear as almost polished for bronze or oil lite applications.

My honest opinion is the shaft and bearing are both not up to the task. Be it finish, hardness or material they are less than what you need. You have a new longer bearing with oiling at pressure, why not acquire an original used shaft to try out? That is the easy fix to accomplish. This eliminates two questionable variables, hardness and finish, possibly even material. Your .004" clearance should work well with pressure.

Make sure the bearing bore surface is smooth with out reamer marks. I'm not sure bronze responds well to hone stones but that would only increase shaft/bore fit making it too big. That shaft is only about 1/2" or there abouts. Glass paper or crocus cloth should work.

[Joe C.]

Re: Distributor Lower Bushing Excessive Wear History

Thanks to all who replied. Distributor is installed. Will drive it for a few hundred miles and take a look.

[Mike E.]

Re: Distributor Lower Bushing Excessive Wear History

The "football" for centrifugal advance, atop the reproduction "SHP" shafts were installed incorrectly by aftermarket suppliers. After notifying all of them last summer, as to this situation, I can report that the condition has been rectified by LICS, but not by Paragon.

Joe
I hope you don't mind me posting in your thread. I'm glad I read this post, I've also been reading an excellent article written by Dave Fiedler (18329). My Tach quit 30 years ago so I knew I was going to have to dig into the distributor plus as many folks have said it can be a neglected part. So no surprise here is what I found. I was all set to order a shaft from Paragon, after reading your post I'll go with one from LIC.



Mike

[Joe L.]

Re: Distributor Lower Bushing Excessive Wear History

Thanks to all who replied. Distributor is installed. Will drive it for a few hundred miles and take a look.

Joe------


Just a follow-up on the distributor gear issue. I see that Comp Cams says that a melonized steel gear (or composite gear) needs to be used with their austempered ductile iron camshafts. That's contradictory to what Speed-Pro/Sealed Power says (or, at least, used to say) about their austempered ductile iron camshafts.

Speed-Pro/Sealed Power was absolutely the first on the market with a retrofit hydraulic roller camshaft. I recall this very well. Way back when, I was absolutely committed to using an hydraulic roller in my small block. However, at that time there were no retrofit set-ups on the market. I kept in touch with all the major cam manufacturers as I was obsessive about getting one as soon as possible. Speed Pro/Sealed Power was the first although the others soon followed (as I recall, Crane was next). The big benefit of Speed-Pro/Sealed Power at the time was that their hydraulic roller retrofit camshafts used an austempered ductile iron core and did not require a bronze distributor gear (which, at that time, the Crane did. I would NEVER, EVER use a bronze distributor gear in a street engine). Later, Crane and some others went to a steel roller cam which had a pressed-on ductile iron camshaft gear. In fact, Speed-Pro definitely stated that a standard distributor drive gear could be used with their austempered ductile iron camshafts and that no "special" gear of any kind was required.

The Speed-Pro retrofit hydraulic roller camshafts were parkerized. I don't know if the Comp Cams cams are so-finished. Although GM cams since time-immemorial have been parkerized, I have not seen any GM hydraulic roller cams that is so-finished. It's possible that the lack of parkerization results in the need to use a melonized (or composite)
distributor gear.

By the way, I'm very reluctant to try a composite distributor gear. While they are quite expensive that's not my issue. They just don't "feel right" to me. Maybe I'm too stuck in old technology.

[Joe C.]

Re: Distributor Lower Bushing Excessive Wear History

Joe------


Just a follow-up on the distributor gear issue. I see that Comp Cams says that a melonized steel gear (or composite gear) needs to be used with their austempered ductile iron camshafts. That's contradictory to what Speed-Pro/Sealed Power says (or, at least, used to say) about their austempered ductile iron camshafts.

Speed-Pro/Sealed Power was absolutely the first on the market with a retrofit hydraulic roller camshaft. I recall this very well. Way back when, I was absolutely committed to using an hydraulic roller in my small block. However, at that time there were no retrofit set-ups on the market. I kept in touch with all the major cam manufacturers as I was obsessive about getting one as soon as possible. Speed Pro/Sealed Power was the first although the others soon followed (as I recall, Crane was next). The big benefit of Speed-Pro/Sealed Power at the time was that their hydraulic roller retrofit camshafts used an austempered ductile iron core and did not require a bronze distributor gear (which, at that time, the Crane did. I would NEVER, EVER use a bronze distributor gear in a street engine). Later, Crane and some others went to a steel roller cam which had a pressed-on ductile iron camshaft gear. In fact, Speed-Pro definitely stated that a standard distributor drive gear could be used with their austempered ductile iron camshafts and that no "special" gear of any kind was required.

The Speed-Pro retrofit hydraulic roller camshafts were parkerized. I don't know if the Comp Cams cams are so-finished. Although GM cams since time-immemorial have been parkerized, I have not seen any GM hydraulic roller cams that is so-finished. It's possible that the lack of parkerization results in the need to use a melonized (or composite)
distributor gear.

By the way, I'm very reluctant to try a composite distributor gear. While they are quite expensive that's not my issue. They just don't "feel right" to me. Maybe I'm too stuck in old technology.

"Parkerized" might just be another name for a surface hardening process. Comp Cams calls it "gas nitride hardening", and they use it on iron cams. I'm not an expert in metallurgy, and although I had a great guy as a college professor, my eyes glazed over. I was of the impression that most flat tappet cams are made of "iron" but nothing special. The cams that we are talking about are the lower performance "street" solid rollers from Comp, like mine, as well as most of their hydraulic rollers, and the ones that you've been referring to from Crane and FM. I'm getting the impression that SADI a tougher version of ductile iron, for more torsional strength, and then a hardened surface is applied to the "iron", whether that be ductile or SADI.

It's in one's best interest to have the cam drive gear be harder than the distributor driven gear. Bronze gears are always referred to as being very short lived, so I agree that they're a poor choice for a street engine. Composite gears go for well over a hundred dollars, so they had BETTER last more than 4x as long as a bronze gear. I'm very glad that I'm not required to use bronze/composite.

A confusing point: "Speed-Pro definitely stated that a standard distributor drive gear could be used with their austempered ductile iron camshafts and that no "special" gear of any kind was required." This is almost a VERBATIM quote to what Comp says about their SADI camshaft gears; however, if your distributor still uses an original iron gear or reproduction thereof, for use with flat tappet camshafts, then THIS type of gear is probably not compatible with an SADI camshaft. This might be one of the reasons that my distributor gear became stepped. It's probable that the verbiage above, which refers to "no special gear of any kind required", is talking about a stock, standard, melonized steel gear that was installed on Corvette distributors after 1986 when GM started installing roller cams.

As already stated, the repop iron gear has a dimple orientation that is "around" 30 degrees different than the GM part AC/Delco 10456413 melonized steel gear.

Here is a handy and informative video on drive/driven distributor gear matings:

http://www.youtube.com/watch?v=31JHSUkhJLY